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From: Joshua Banton <[email protected]>
To: Dirschel, Steve-CW <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Troubleshooting a brief spike in active sessions
Date: Fri, 9 Jan 2026 16:58:57 -0500
Message-ID: <CAHkYM9bP5izAeh_JF1PqM6v4HVfQOgeEmCQF0i63oJFFwnUsdA@mail.gmail.com> (raw)
In-Reply-To: <BL0PR06MB5009A7B383ACA34CD3603B058A82A@BL0PR06MB5009.namprd06.prod.outlook.com>
References: <BL0PR06MB5009A7B383ACA34CD3603B058A82A@BL0PR06MB5009.namprd06.prod.outlook.com>

On Fri, Jan 9, 2026 at 4:41 PM Dirschel, Steve-CW <
[email protected]> wrote:

> Aurora Postgres version 17.4
>
> This application mainly runs 3 queries very frequently-  around 12000
> executions per second across the 3.  Normally the server handles this fine
> and at any given time there are between 0 - 10 active sessions running the
> queries.  The 3 queries are tuned-  doing 3-7 logical reads per execute and
> run in < .1 millisecond.
>
> Periodically there will be a huge spike in active sessions up to 400+
> sessions all on CPU (it can be higher depending on how many app servers are
> in the mix at the time).  This spike will last 2-5 seconds but it causes an
> increase in app response time which is a problem.
>

I'm not super familiar with Aurora, but I've seen this caused by a few
different things in vanilla Postgres. I don't think Aurora has checkpoints,
so it's probably not that. I have seen where a vacuum can cause various
Postgres buffers to have a lot of churn, which can cause higher query
latency for a period of time. I have also seen temporary increased disk
latency to cause higher query latency.

Josh B

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